Diaphragm cover for liquid storage tanks



DIAPHRAGM COVER FOR LIQUID STORAGE TANKS 27 23 24 l 23 4 23 28 Y 2 A\ j 2 2l I l 2| I9 I9 I9 f 262B 25 23 23 22 FIG 2 22 l 36 F|G.3.

'5 32 INVENTOR.

35\ N, FRED L. PLUMMER,

k BY F|G,4.. P33 25 302 o l: n un 54/2 La' ATTORNEY Dec. l1, 1951 F. L. PLUMMER DIAPHRAGM COVER FOR LIQUID STORAGE TANKS Filed April 17. 1948 FIG.7.

4 Sheets-Sheet 2 INVENTORZ FRED L. PLUMMER, BY

ATTORNEY Dec l1, 1951 F, PLUMMER 2,578,090

DIAPHRAGM COVER FOR LIQUID STORAGE TANKS Filed April 1'?, 1948 4 Sheets-Sheet 3 INVENTOR:

FRED L. PLUMMER,

ATTORNEY Dec. 11, 1951 F. PLUMMER 2,578,090

OIARHRAGM cOvER ROR LIQUID STORAGE TANKS Filed April 17, 194e 4 sheets-sheet 4 F I G. I4.

FIG. I6.

'5; MMM L|L||' j l l l v 4b' 22 =\42 FIG. l?. F22? 4;

l l I I I I INVENTOR w FRED L. PLUMMER, BY ma.

ATTORN EY Patented Dec. 11, 1951 Fred L. Plummer, Warren, Pa., asslgnr`to'Hammond Iron Works, Warren, "Parfacorporation 'of Pennsylvania Application April 17, 194s, serial No. 21,603 1 claim. (ci. 22o-ass) 1 r Thisinvention relates to "closed liquid-storage metallictanks more particularly of the type that i's 'adapted to hold volatileliquids such as are derived from petroleum, or the ltype of high octane gasoline, and in which tank the amount of the liquid stored-therein fluctuaties so 'that the liquid-level in the tank varies. Itis an object of this invention -toeiiminate 'from such tanks all major vaporreceiving'ior accumulating air spaces for thereby preventing the formation of an airvapormixture of alllirc'iu'ids havinga vapor-pressure less than atmospheric pressure so no gases arek formedwhich can escape. It is a further object vof this invention to ydevise an impervious flexible diaphragm that is at all times in contact with the liquid-level of a liquid stored in the tank, whose purpose is `to`prevent the escape of gas that may'have become volatilized from the liquid and also to prevent lcontaminants from getting into the liquid. To that end, it is proposed tosupport a 'generally bucket-shaped diaphragm from the inner wall ofV the tank at an elevation intermediate the height of the tank wal-1, but to so support the diaphragm that itsv bottom closure section rises and falls ywith the rise and fall of the liquid-level in the tank yet without causing disruptive friction between the cylindrical ortubular side-wall section of the diaphragm and themetaliic tank wall. I

When the tank is substantially empty of liquid, the bucket-shaped diaphragm hangs or depends from its wall support, and it takes its normal bucket-shaped form or contour. But as the liquid-level rises in the tank and the bottom section of the diaphragm rises therewith, provision must be made for taking uporall'owing for" the folding of the excess material of Athe diaphragm, so it is another object of this invention so to arrange and design the diaphragm vthat* this excess material will be taken up or form a dependin g main deformation fold and the folding thereof is to be controlled so that it is of generally substantially continuous annular extent or pattern while being 'so disposed 'that it vis alwayshlo'- cated at a distance fromjthetajnk wall, in other words, that the deformation 'pattern or patterns are always in the bottom section of the diaphrag'm.y Another object is to prevent as far as possible th'e sides of the diaphragmvf'rom coming into contact with the tank wall while the bottom sect-ionvofthe diaphragm is below' the circumfer@ entrai une of. support-of the; diaphragm wan. A still 4further object' is to design such a diaphragm that as its bottom section ri's'efs above the lineof" support of the Vdiapl'iragin walls; that part of the diaphragm'walls which comes `'into Contact with the tank "wall will contact the tank wall in 'a' rolling-on ff'ashion, and when leaving the tank wallwill'leave it in a peeling-off fashion. This" designed tanks as is `now necessary. In other" words, :this type of diaphragm oies a cheap'and effective way ofuooverting present non-appro priat'e 'tanks into tanks 'that are 'highly appropriate to Store' valuable Volatile liquids. y

The` Ybest embodiment of the invention now known to fine has ybeen chosen for illustrative purposes, but this embodiment should, be viewed as 'being illustrative'only and 'not as limiting because vobviously the invention is capable of other embodiments having fr'evised details and construction, so vlong as they fall 4within the ambit of trie Aappendedclaim. Y i

The invention isill'ustrated vin the accompanying drawings 'in which Fig. l'shows a vertical sectional view through a tank 'equipped with ,the diaphragm `rof this invention. Variant positions taken hy the diaphragm are shown in broken lines. Fig. 2 a partial isometric viewA of the diaphragm rwith parts thereof broken away so that its interior construction may beseen. Fig. 3 is another partial sectional isometric view of the diaphragm 'with parts broken away to show the coter-istrip arrangeine/ni, for securing together abutting "edges of the flexible material of the bottom sections. Fig. 4 is a partial vertical sectional view showing the construction of the diaphragm-supporting rim on the interior of the tank with the *means `ior fastening the free o r upper edge' of the diaphragm thereto. Figo is a partial sectional and'isometric view through a section' of th' 'annular fold'that develops in thewardly vat the diaphragm' from the bottom'qwhile .me `position as in Fig. 6; Figs. 8,

it isfi'n'thel n similar sectional isometric views 9 'and 10 snowing4 the diaphragm inv three different pesi:

tinstiowjthediaphragimsupportmg rim, while Figs. 11; 12' and lf3 Lare somewhat similar views showing three diiferent positions of the diaphragm above the diaphragm-supporting rim. Fig. 14 is a partial sectional view showing how the wall-section of the diaphragm rolls on or against the tank wall when it is above that diaphragm-supporting rim, while Fig. l5 is a similar view but vshowing the peeling-ufff.` action that takes place when the diaphragm wall leaves the wall of the tank. Fig. 16 is a vertical sectional view through the tank showing one lower variant position of the diaphragm when weighting water- Y the diaphragm will then take a position and form or other liquid is supplied and vcarried by the 1 upper surface of the diaphragm, while Fig. 17 is a similar view but with the diaphragm in an upper variant position and shows the Vwater-nlm that forms between the wall of the diaphragm and the wall of the tank.

In the drawings, and particularlyl Fig. 1 thereof,A

I| indicates a liquid-holding metallic tank hav-l ing a bottom I2, side wall I3, and top I4, which when of larger diameters such as more than 50 feet may be trussed as at l5 should the size of the tank warrant it. Such tanks are usually vented as for instance at I6 or some eouivalent thereof. The tank can be filled with'liduid, or liquid withdrawn therefrom by some suitable pipe or conduit Just above the horizontal center or median of the tank there is provided a substantially annular support or rim I8 from which is hung a bag-like or bucket-shaped diaphragm indicated generally by the numeral 2li having side walls or a tubular side wall section 2| and a bottom or bottom-closure section 22. The diaphragm is made of flexible gasand liquid-impervious material such as liquidand gas-proofed :i

fabric but preferably nylon cloth coated on both sides with a synthetic rubber material such as neoprene or Buna-N-type. The walls can be made of vertically extending strips I9 secured together (Fig. 2). The bottom 22 comprises a disc-like piece of such flexible material formed of strips 23 of such material suitably secured together to form the bottom, with the abutting edges of such strips cemented together and preferably with cover-strips 24. The periphery or if peripheral edge 25 of the bottom 22 issecured or cemented to the lower edge 26 of the side walls 2| of the diaphragm 2D by weighting means comprising joint-covering devices such as annular upper cover-strips 21 and an annular lower cov- :,f, walls 2| is greater than the diameter of the correer-strip 28, both covering and protecting the juncture of the abutting edges 25 and 26. The diaphragm-support numbered generally as I8 is shown in detail in Fig. 4 wherein it can be seen that this assembly comprises a substantially ano nularly extending angle iron 3|) having a horizontal portion 3| and a vertical flange or rim portion 32. The horizontal portion 3| is secured to the inside of the tank'wall I3 by means of an upper weld 33 and a lower weld 34. A further weld 35 is provided against which bears or is jammed a lead or other deformable strip 35 for frictionally securing in place in supporting position the upper or free end of the walls 2| of the diaphragm 2t. I

Fig. 1 shows the parts with little or no liouid in the tank II so that the diaphragm hangs from its support I8 in a true bucket-like shape or formation and in position A'. Suppose now that enough liquid is pumped into the tank beneath the bottom 22 of the diaphragmto provide enough liquid-pressure exerted on the diaphragm bottom from below to cause that bottom to be raised by its floating contact with the liquid-level of the liquid so that the diaphragm will then asy indicated in Fig.l l as at A'".

Position A is shown in greater detail in Fig. 8, position A" in Fig. 9 and position-A" in Fig. 10-all being at or below the elevation of the diaphragm-supporting rim or iiange E8. It will be noted that thel annularly, extending fold 4|! progressively I elongates downwardly as these rising positions are taken; that the dual cover-strips 2 and 28 always seem to be at the bottom of the fold, and that in these variant positions the wall section 2| of the diaphragm 2B is drawn away or spaced .from the side wall 3 of the tank I I. As the diaphragm passes from position A to A", and from A to A", for instance, the diameter of the annular fold, or more particularly the annular cover-strips 21 and 2S, must diminish. This lessened diameter is accomplished by increased irregularity or by folding or undulating both vertically and circumferentially of the fold 4B, as is attempted to be illustrated in Figs. 5 and 6, but especially in Fig. 7 which is a view looking up at the fold from beneath the diaphragm. Indeed, smaller or minor folds are superposed on the larger or main annular fold 48 so that the latter becomes what may be termed a composite fold.

However, as the liquid-level rises further and lifts the bottom 22 of the diaphragm to an elevation above that of the ange I8, a slightly different condition exists. Dotted line position B in Fig. 1 shows the new` condition, namely that the upwardly extending portion of a section of the diaphragm walls 2| is in actual contact with tank wall I3. This condition continues as the next higher position B" is assumed, and in its highest position B". Position B' is shown in enlarged detail in Fig. ll, B" in Fig. l2 and B" in Fig. 13. In other words, the diameter of the upwardly extending section of the diaphragm spending section of the same walls when they are in depending position instead of upwardly extending, that is when they are below the diaphragm-support I8. However, even in the upper positions B' and B" the same annular folding 4Q takes place. When the diaphragm is raised or lifted by liouid therebeneath to an elevation above the support I8, that section of the diaphragm walls 2| that comes into contact with the tank wall I3 does so in a rolling-on fashion as shown in Fig. 14 (indicated by arrows) so there is a minimum of rubbing friction between the two. On the other hand, when the liquid-level begins to fall and the diaphragm bott/om goes from position B" to position.B"., or from B" to B', that part of the diaphragm wall that is in contact with the tank wall leaves the latter in a peeling-off fashion, as shown in Fig. 15 (indicated by arrows), for similarly minimizing friction or rubbing. In smaller diameter tanks using a self-supporting dome roof without truss supports the full capacity of the tank can be used by having the diaphragm, when in position B'". bear against the dome roof.

The path taken by the substantially annular fold 40, whosegeneralannularityof*pattern in planfview is shown in Fig, .6, however irregular iii-maybe in practice, is a curved line, showniby theidotFand-dash line C in Fig'. :land probably generally parabolic. This is because =the dia- Dhragrnmust telescope in its diameter `asis'assumes, positions anywhere between its extreme upper and flower positions. .The-:path above `the diaphragm-supporting rim has a differentfcurva'- tune, fromthat part of the path .therebelow VThe reason is because the diameter assumed by the diaphragm when above the supporting rim is greater than when the diaphragm is therebelow.

It will be seen from Figs. 1, 5 to 7, and 9 to 12, that the wall section 2i of the diaphragm assumes an angular formation in all but its extreme upper and lower positions. That is, the wall section has a vertical section adjacent the support devices that then merges into, or has derived therefrom, a generally horizontal annular spacing section lying between the fold and the vertical section.

Since an important feature of this invention is the control of the folding of the diaphragm so that it assumes localized substantial annularity, which control is exercised by particularized weighting, other weighting means obviously can be used or substituted for the cover-strip arrangement 21 and 28 so long as they produce the substantially annular folding or deformation pattern in the bottom of the diaphragm. For instance, it is possible to use a single cover-strip instead of two superposed strips such as 21 and 28, and sometimes it may be desirable merely to lap adjacent edges of pieces or strips of the fabric of the bottom. Also this centralizing of the folding can be emphasized by the use of a quantity of weighting liquid on top of the diaphragm bottom 22. Fig. 16 shows how such liquid 4l acts when the diaphragm assumes a position such as position A, while Fig. 17 shows how such liquidV 4I acts when the diaphragm assumes such a position as B". The liquid may be water, or a salt solution, or indeed any liquid that tends to emphasize the fold 4). A sufficient quantity of such weighting liquid 4l can be used so that when the diaphragm assumes an upper position, such as B", some of the liquid will run over and down the side walls 2| of the diaphragm to reside between those walls and the walls of the tank, as shown in Fig. 17, where it serves as a friction-preventing film or layer 42.

It is sometimes desirable to supply a valve controlled pipe 44 in the side wall I3 of the tank and just below the diaphragm-support I8 provided so that before liquid is pumped into the tank most an excess volume of air and vapor if air should f be introduced by pumping through the inlet to the tank. It would not generally be used because of volatilization of the liquid stored in the tank.

Thus the invention can be practiced by providing a support for the free edge or open end of the bucket-shaped diaphragm so that the diaphragm hangs or depends from that support in a position that when the tank is empty the bottom closure or end of the diaphragm approximates but does not actually touch the bottom of the tank.

Fold-inducing means are provided to operate when the bottom of the diaphragm rises due to rise of the liquid-level in the tank. That is the necessary folding of the bottom to accomplish 6. the 'necessary shortening thereof is centralized or rlocalized by the weighting cover-strips. The folds must take place somewhere so they seem to be induced or controlled to take place in more'or less general alignment with these strips and as an increasing Vamount of excess material hasto be taken up the 'general fold 4D becomes a comf posite one with smaller folds superposed on the larger one. Further, the general fold is thus caused always to depend from the diaphragm bottom lin `a more `^or yless annular pattern downwardly into the liquid in the tank, and this seems to pull the wall ofthe diaphragm away from the tank wall, .at least until the diaphragm vbottom reaches an elevation equal to l'the diaphragmsupport on the tank.

But when the bottom of the diaphragm rises to an elevation above that support, the reverse seems to happen, namely, the walls of the diaphragm are allowed to be pressed against the wall of the tank in a gentle progressive manner that can best be described by saying that it takes place in a rolling-on manner that is substantially frictionless. This rolling-on is found to be substantially nonwrinkle-forming as the wall of the diaphragm fits the tank wall snugly and very smoothly.

When the liquid-level in the tank falls, the diaphragm walls leave the tank wall in a curving or peeling-off manner as the dependent folds increase in depth, and when the diaphragm bottom gets below the level of the supporting rim, the diaphragm walls are again maintained out of contact with the tank wall.

This functioning is satisfactory but under certain circumstances it may be desirable to supply and maintain a liquid on top of the diaphragm bottom. This liquid seems to equalize to some extent the hydraulic pressure on both sides of the diaphragm bottom in that the stored liquid pressing upwardly from beneath and the liquid on top pressing downwardly results in a pattern taken by the folds which is much more regular and more accurately localized or centralized about the cover-strips at the juncture of the diaphragm bottom and walls. Another advantage of the use of such liquid is that when the diaphragm rises above the supporting rim and its walls tend to be pressed against the tank wall, there is a film of this liquid therebetween which tends to lubricate the contacting parts to be quite frictionless.

What I claim is:

In combination with a liquid storage tank adapted to have the liquid level therein vary, a diaphragm construction comprising impervious flexible material adapted to have Contact with the liquid and to adapt itself to variations of the liquid level, and fastening means extending inf ternally along the periphery of the vertical tank wall at an intermediate elevation thereof for fastening the peripheral edge portion of the diaphragm to the tank; characterized by the fact that the diaphragm comprises a vertical cylindrical portion extending from said fastening means along the vertical tank wall, an annular portion extending in a horizontal plane inwardly from said cylindrical portion and in the plane of the liquid level, a central circular portion surrounded by and co-planar with said annular portion, and a depending annular fold connecting said annular portion with said central portion, said annular fold being adapted to assume a smallest diameter, a greatest depth, and a greatest distance from the tank wall when the liquid level substantially coincides with the elevation of the fastening means While `the height of the cylindrical portion becomes a minimum, said diameter being adapted to increase as the liquid level rises or falls with respect to said elevation With a concomitant compensatory decrease in depth of the fold, a compensatory decrease of distance between the fold and the tank wall, and a compensatory increase of height of said cylindrical portion.

FRED L. PLUMMER.

REFERENCES CITED The following references are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Glass June 14, 1927 Weichsel June 3, 1939 Ellis Apr. 1, 1941 Ellis Oct. 7, 1941 Wilkin Jan. 13, 1942 Wiggins Oct. 1, 1946 Feild Feb. 15, 1949 Allen Dec. 13, 1949 

